1. Field of the Invention
The present invention relates to a composite construction of pipe for use in the oil, gas, water and chemical industries.
2. Description of Prior Art
It is known to manufacture pipe by the helical winding of a plurality of metal strips and which strips are embedded in a plastics material matrix.
U.S. Pat. No. 4,657,049 describes the manufacture of such pipe by helically winding at least one metallic reinforcing strip onto a mandrel, the strip being coated with and embedded within a polymeric bonding material. The tube is thus formed of a plurality of successive helical convolutions of metal strip, completely embedded in the polymeric material. In this construction the polymeric material provides only a limited degree of corrosion resistance and hence is not suitable for many pipe applications.
U.S. Pat. No. 4,351,364 describes a similar method of tube construction, but the tube also has inner and outer linings of resin impregnated glass-fibre layers. The glass-fibre layers comprise woven cloth and chopped fibre strand mat. The purpose of the inner lining is to provide corrosion resistance and a low flow resistance, whilst the purpose of the outer lining is to provide resistance to environmental conditions. Whilst the glass-fibre reinforced linings on the inside and outside of the pipe enhance the resistance to corrosion, abrasion and other environmental conditions, they do not significantly improve the strength of the pipe, nor do they provide optimum corrosion resistance owing to the porosity which is inevitably retained within the glass fibre mat and cloth.